Benign Bone Tumors

Snapshot

• A 12-year-old boy develops mild pain in his right leg. The pain is worse at night and improves with aspirin. A radiograph of the right leg is shown demonstrating a small mass with a radiolucent nidus surrounded by reactive bone. The patient is subsequently diagnosed with an osteoid osteoma. 

Osteoma

• Definition
  • benign bone tumor (osteogenic) derived from osteoblasts
• Presentation
  • location
    • skull
    • mandible
  • symptoms
    • painless mass
  • associated conditions
    • Gardner syndrome
• Associated findings
  • histology
    • proliferating osteoblasts with active intramembranous ossification
  • radiography
• radiodense and smooth bony mass 

Osteoid Osteoma

• Definition
  • benign bone tumor (osteogenic) derived from osteoblasts
  • small (< 2 cm)
• Presentation
  • location
    • proximal femur (most common)
    • tibial diaphysis
    • vertebrae
  • symptoms
    • focal pain that resolves with NSAIDs
    • if arising in the spine, may cause painful scoliosis
• Associated findings
  • histology
    • nidus of osteoid and immature osteoblasts surrounded by a rim of reactive bone formation
  • radiography
• radiolucent nidus (< 2 cm) surrounded by reactive bone 

Osteoblastoma

• Definition
  • benign but locally aggressive bone tumor (osteogenic) derived from osteoblasts
  • larger than an osteoid osteoma (> 2 cm)
• Presentation
  • location
    • vertebrae (most common)
    • long bone diaphyses
  • symptoms
    • focal pain that is not relieved by NSAIDs
    • if arising in the spine, may cause neurologic symptoms
• Associated findings
  • histology
    • nidus of osteoid and immature osteoblasts surrounded by a rim of reactive bone formation 
  • radiography
    • radiolucent nidus (> 2 cm) surrounded by reactive bone 
• large lesions may extend into soft tissues

Giant Cell Tumor (Osteoclastoma)

• Definition
  • benign but locally aggressive tumor derived from stromal cells with accompanying giant cells
    • stromal cells resemble interstitial fibroblasts and are neoplastic cells
    • giant cells are derived from monocyte/macrophage lineage and have similar characteristics to osteoclasts
• Presentation
  • location
    • metaphyseal regions of long bones
      • distal femur (most common)
      • proximal tibia
      • distal radius
  • symptoms
    • focal pain
      • may be referred to nearby joint
• Associated findings
  • histology
    • 3 cells types may be seen 
      • stromal cells resembling fibroblasts
        • neoplastic cells
      • monocyte/macrophage cells recruited from peripheral blood
        • precursors to giant cells
      • giant cells
        • multiple nuclei
        • similar to osteoclasts
        • resorb bone
  • radiography 
    • an eccentric lytic metaphyseal lesion that may extend into the distal epiphysis
    • characteristic “double bubble” or “soap bubble” appearance
• increased activity of osteoclasts results in a cavitary lesion 

Osteochondroma (Exostosis)

• Definition
  • benign cartilage-derived tumor (chondrogenic) containing bone and a cartilage cap
    • arises as a lateral projection of the growth plate
  • most common cartilage-derived tumor
  • two forms
    • solitary osteochondroma
      • may be caused by Salter-Harris fracture, surgery, or radiation therapy
    • syndromatic osteochondromas
      • multiple hereditary exostosis (MHE)
• Presentation
  • location
    • metaphyseal regions of long bones
      • distal femur
      • proximal tibia
      • proximal humerus
  • symptoms
    • painless mass
• Associated findings
  • histology
    • normal bony trabeculae with a thin cartilaginous cap 
  • radiography
• sessile (broad base) or pedunculated (narrow stalk) lesions found on the surface of bones 

Enchondroma

• Definition
  • benign cartilage-derived (chondrogenic) tumor
    • arises when chondroblasts and epiphyseal cartilage escape from the physis, enter the metaphysis, and proliferate
  • second most common cartilage-derived tumor
  • two forms 
    • solitary enchondroma
    • syndromatic enchondromas
      • Ollier disease
      • Maffucci syndrome
• Presentation
  • location
    • medullary cavity in the metaphyseal or diaphyseal regions
      • hand (most common)
      • feet
      • distal femur
  • symptoms
    • most often asymptomatic
    • pathologic fracture
• Associated findings
  • histology
    • bland mature hyaline cartilage
  • radiography
    • well-defined lucent medullary lesion